Koalas Can Recover Genetic Diversity After Bottlenecks

Koalas in Australia once faced a dramatic population collapse due to hunting, disease and widespread habitat loss. But a new study suggests the iconic marsupial may still have a path toward recovering its genetic diversity—even after experiencing severe population bottlenecks.

Research published in March 2026 in the journal Science analyzed the genomes of hundreds of koalas across Australia to understand how the species recovered after periods when their numbers dropped sharply. The study examines what scientists call a genetic bottleneck, a situation in which a population shrinks so drastically that only a small number of individuals remain, dramatically reducing genetic variation.

A genetic bottleneck can have long-lasting consequences for wildlife populations. When only a few individuals survive, most of the species’ genetic variation disappears because only the genes carried by those survivors are passed on to the next generation.

For the Koala, this happened during the late nineteenth and early twentieth centuries. During that period, millions of koalas were hunted for their fur across Australia, pushing the species close to extinction in several regions.

In response, conservationists relocated small groups of surviving animals to repopulate areas where koalas had vanished. While these efforts helped restore numbers, many of the new populations were founded by only a handful of individuals, raising concerns about extremely low genetic diversity.

Low diversity can increase vulnerability to disease, genetic disorders and environmental change, making long-term survival more uncertain.

Genome Study of Hundreds of Koalas

To investigate how koalas have fared genetically since then, scientists conducted a large-scale genomic analysis. The team examined DNA from 418 individuals collected from 27 populations across Australia.

The research was led by scientists from University of Sydney, including lead author Kylie Cairns. By comparing genetic variation among populations, the researchers were able to reconstruct how koala populations changed over time.

The results surprised the team. Despite experiencing severe genetic bottlenecks, some koala populations showed signs of recovering genetic diversity more quickly than scientists had previously expected.

“When populations grow rapidly again, genetic recombination can reshuffle the remaining variation and generate new combinations of genes,” Cairns said in a statement accompanying the study. “That process helps rebuild some of the genetic diversity that was lost during the bottleneck.”

How Population Growth Helps Genetic Recovery

One of the study’s central findings is that rapid population growth plays a key role in restoring genetic variation.

As populations expand, reproduction creates more opportunities for recombination—the biological process in which segments of DNA from both parents mix during the formation of offspring. Over time, this reshuffling can produce new genetic combinations and increase diversity within a population.

Senior author Marc Johnson said the findings suggest that genetic bottlenecks do not necessarily doom a species to permanent genetic decline.

“Species that pass through severe population crashes are not always trapped in an irreversible genetic downward spiral,” Johnson said. “If the population rebounds quickly enough, evolutionary processes can still rebuild some of that lost diversity.”

However, the researchers emphasize that genetic recovery has limits. Some genetic variants lost during a bottleneck may never return, meaning that recovered populations may still carry a legacy of reduced diversity.

Implications for Wildlife Conservation

The study offers broader lessons for conservation efforts worldwide. Many wildlife species today face population declines driven by habitat destruction, climate change and human activity.

The new findings suggest that boosting population size can play an important role not only in saving species numerically but also in helping them recover genetically.

For koalas, however, major threats remain. Habitat loss from urban development, disease such as chlamydia infections and increasingly intense wildfires continue to pressure populations across Australia.

In recent years, large bushfires have destroyed vast areas of eucalyptus forest, the primary food source for koalas. These environmental pressures highlight the importance of protecting habitats while also maintaining healthy population sizes.

Genomic studies like this one can help conservation managers design more effective strategies. By understanding the genetic relationships among populations, scientists can determine whether moving individuals between regions might help boost genetic diversity.

Cairns said conservation efforts must focus on more than simply preventing extinction.

“Protecting a few surviving animals is not enough,” she said. “We need populations that are large and connected enough for natural evolutionary processes to restore their genetic health.”

The findings provide cautious optimism for one of Australia’s most recognizable species. Even after severe population crashes, koalas may retain the capacity to recover genetically—provided their habitats are preserved and their populations are allowed to grow.

But scientists warn that this recovery depends on continued conservation efforts. Without protected forests and stable populations, the evolutionary mechanisms that help rebuild genetic diversity may not have the chance to work. (Wage Erlangga)